In general, in the case of a mobile information terminal such as a mobile phone or a PDA (Personal Digital Assistant), at the time of entering characters, it is not easy to restore a once-fixed character string to a state before the fixation to perform editing. For example, in the case of entering numbers into an entry form on a website, if a character string fixed as full-width characters is desired to be changed to half-width characters, the half-width characters should be reentered after deletion of the character string.
On the other hand, recently, a technique of performing pinch operation using a thumb and an index finger, called pinch in operation, on a touch panel to thereby zoom out (reduce) a displayed image, and performing enlarging operation called pinch out operation on the touch panel to thereby zoom in (enlarge) the displayed image has been proposed (e.g., Patent Document 1). Accordingly, if by performing the pinch in or pinch out operation on a display screen for displaying character strings, the selection of a character string of which a character type or the like is desired to be changed and a conversion process of the selected character string can be performed, an editing task of character strings can be facilitated and also intuitively performed.